The method of producing a regenerated cellulose sponge



United States Patent ()fiiee aliases Patented Nov. 12, T1963 3,110,692 THE NEETHGD OR PRODUCING A REGENERATED CELLULGSE SPONGE Alfred llolitzer, Cleveland, James C. H. Tang, Farms, and Trilochan Singh, Cleveland, Ghio, assignors to Nylonge Corporation, Cleveland, Ghio, a corporation of Qhio No Drawing. Filed Apr. 2.6, H60, Ser. No. 23,349

9 (Zlahns. (Cl. 1456-122) The present invention relates generally to an improved method for the production of sponge masses, and it relates more particularly to an improved method for producing a fiber reinforced, viscose regenerated cellulose sponge of improved physical properties and to an improved regenerated cellulose sponge.

In accordance with the conventional method of producing regenerated cellulose sponge by theviscose process, a high alpha cellulose pulp is alkalized in the well known manner, admixed without aging with carbon bisulfide to produce cellulose xanthate, which in turn is dissolved in a weak alkaline solution to form viscose of the desired composition. The viscose is admixed with cut and opened reinforcing fibers and a water soluble pore-forming substance such as sodium sulphate decahydrate, and the resulting mass is treated to coagulate the viscose and regenerate the cellulose. This may be done by an acid solution or heated by means of hot sodium fulfate solution, high pressure steam or by electrical resistance heating of the viscose mass. The pore-forming substance is then removed and the sponge is washed, bleached, plasticized and dried and cut. It is then ready for packaging or use.

The time, power and materials consumed by the conventional method of producing regenerated cellulose sponge are considerable and are greatly reflected in the high cost of the finished sponge. For example, it required at least approximately seven hours for the purification, bleaching and plasticizing of the sponge alone. Moreover, the final product is often deficient and lack- .in many of its physical requirements. The water absorbency of the sponge is less than desirable. The sponge is often characterized by the agglomeration of the fibers into nodules or bundles dispersed throughout the sponge to render the sponge inferior in quality and acceptance. Another undesirable characteristic usually met with is the presence of large voids, which are formed by the formation of large gas bubbles during the production and coagulation of the sponge-forming mass.

It is thus a principal object of the present invention to provide an improved method for the production of artificial sponges and the resulting product.

Another object of the present invention is to provide an improved method of producing regenerated cellulose sponges by the viscose process and the resulting product.

Still another object of the present invention is to provide improved fiber reinforced regenerated cellulose sponges and an improved method of producing the same by the viscose process.

A further object of the present invention is to provide an improved method of producing fiber reinforced regenerated cellulose sponge by the viscose process, said method being characterized by the reduction in the consumption of time, labor, power and raw materials and the consequent reduction in the cost of the final product.

Still a further object of the present invention is to provide improved fiber reinforced regenerated cellulose sponges and a process of producing the same by the viscose method, the sponges being characterized by their greater absorbency, uniform distribution of reinforcing fibers, absence of large voids and superior strength and other physical characteristics and by their lower cost.

In order to produce a regenerated cellulose sponge of satisfactory and acceptable strength, it is necessary to reinforce the sponge with fibers uniformly distributed therethrough. These fibers have generally been hemp or flax, and their uniform dispersion throughout the sponge mass has been very difficult and it is common to find large aggregations and clumps of fibers which reduce the acceptability of the sponge. This agglomeration occurs during the admixture of the fibers with the viscose and is experienced even when the fibers are introduced in a completely open separated and fluffy condition.

Furthermore hemp and flax are relatively expensive and represent a considerable fraction of the cost of the raw materials employed in the production of the sponge. Although other reinforcing fiber, both natural and synthetic, have been proposed, such as nylon, cotton, rayon, polyester fibers and the like, they possess many drawbacks and disadvantages and have not been generally employed.

It has been discovered that when the reinforcing fibers are first dispersed in 'an aqueous solution of a compatible wetting agent and the aqueous dispersion introduced into the viscose, a uniform distribution of the fibers in the sponge mass is achieved. The conventional methods heretofore employed in distributing the reinforcing fibers in the viscose mass resulted in the occurrence of fiber lumps in 25% to of the final sponge product. Such sponge is of little commercial value and represents a great loss. 'In contrast, by employing the process of the present invention the sponge yield without any trace whatsoever of fiber lumps has been substantially Moreover, it has been further discovered that the reinforcing material may be derived in whole or in part from cellulose pulp in sheet or bulk form and introduced in the above manner. Where a cellulose pulp is so employed in Whole or in part as the source or the reinforcing material, additional appreciable reductions in the cost of the raw materials and final sponge are realized.

As a consequence of employing the procedure above set forth many other unexpected and highly advantageous results have been realized, both in the method of manufacture and in the end product. The coagulated sponge mass produced by the present method is characterized by its greatly increased permeability and penatrability. Since the freshly coagulated sponge mass must be thoroughly washed to completely remove the pore-forming substances and the various by-products and other contaminants, such as sulphur and sulphur compounds, etc., the rate of treatment is a function of the permeability of the sponge mass. In actual commercial practice the time consumed in effecting the washing, bleaching and plasticizing of the sponge was reduced to half the conventional practice without any sacrifice in effectiveness. Another unexpected result was the greatly increased absorbency of the sponge. Without the employment of the fiber pretreatment step the sponge is normally capable of absorbing on the average of approximately 15 times its weight in Water, whereas Where the pretreatment and carry-over of wetting agent with the fibers is employed the water absorbency of the fiinished sponge is as high as 25 times or more its original dry weight. Moreover, the improved sponge is radically softer than the sponges produced by the conventional methods. These improved characteristics are accomplished Without any sacrifice in thestrength and wearing properties of the sponge. Another unexpected result is the absence of large voids in the improved sponge. During the manufacture of the sponge, the sponge-forming viscose mass is kneaded and considerable air bubbles are entrained in the mass. Further, during the coagulation of the viscose gas bubbles are evolved. Thesebubbles often conglomerate to form larger bubbles, resulting in large voids throughout the sponge mass, which greatly detracts fromits usefulness and acceptability. By use of the wetting agent in the manner set forth, any bubbles that may be formed are relatively small and uniformly distributed and do not collect into large bubbles and form the consequent large undesirable voids.

Examples of wetting agents which may be employed to great advantage in the present process are Nopco GLN and Nopco 1179. GLN is diethanolamine of caproic acid and Nopco 1179 is lauryl alkylol amide. Other wetting agents which are compatible with viscose may be employed and are preferably of a cationic or nonionic nature such as, for exarnple, quaternary ammonium compounds, polyether alcohols, aryl polyether sulphates, etc. The concentration of the aqueous solution of the wetting agent employed in pretreating the fiber is highly important and should be at least 0.1% and preferably between 0.1% and 1%. The amount of the wetting agent introduced with the dispersion into the viscose is likewise of importance. This introduction of wetting agent should be at least 0.20% of the cellulose content of the viscose and should preferably not exceed 3.2% thereof and the ratio of the wetting agent solution to the fibers should preferably be between 3:1 to 9:1, advantageously between 4:1 and 8:1. Furthermore, the water carry-over into the viscose should be considered in producing the viscose as to the composition thereof.

As a specific example of the improved process, a green viscose having a high salt point, for example, in excess of 16 salt point, and a cellulose content of 8%, having a high degree of polymerization is produced in accordance with well known methods. Sheets of cellulose con-' taining between 40 and 50 pounds cellulose, for example, 45 pounds cellulose are steeped in an approximately 18 /z% sodium hydroxide solution for a time sufiicient to convert the cellulose into alkali cellulose. The excess sodium hydroxide solution is then pressed from the resulting alkali cellulose in the conventional manner and the unaged alkali cellulose is admixed with between 15 and 27 pounds of carbon bisulfide, and the resulting mixture is tumbled in a suitable drum until cellulose xanthate is produced in accordance with the general practice. The resulting cellulose xanthate is dissolved in a weak sodium hydroxide solution in an amount to produce approximately 600 pounds of viscose having an analysis of between 6% and 8% cellulose, for example, 7.6% cellulose, to 7% of total alkalinity, for example, 7% and between 3.3% and 3.6% total sulphur, for example, 3.3%.

From 10 to 20 pounds, for example, pounds of cut flax or other fiber, as aforesaid, having a fiber length of from /5 inch to 1%. inch, for example, inch is immersed in 8 to 18 gallons aqueous solution of the wetting agent depending upon the nature of the fibers and in the range of concentration as aforesaid, for example 0.2% solution of Nopco GLN at room temperature for a period exceeding 5 minutes, for example, 15 minutes.

To the 600 pounds of viscose in a green unripencd condition hauing a viscosity of approximately 200 seconds, as measured by the fall in the viscose for 8 inches of a 4 inch diameter ball, the viscose containing suitable dyestulf, is then added the above prepared fiber containing wetting agent solution in toto, and thorough mixing thereof is effected, preferably by means of a double delta blade mixing machine while maintaining the mass at a temperature not exceeding 15 C. This initial mixing period is preferably in excess of 20 minutes, for example, minutes. To the resulting mass is added between 1000 and 2500 pounds, for example, 1700 pounds of sodium sulfate decahydrate crystals having an average particle size in accordance with the desired pore size of the finished sponge. For example, average particle size of about 10 millimeters will produce a relatively coarse pore sponge, whereas an average particle size of about 2 millimeters will produce a relatively fine pore sponge. The mixing is then continued for approximately 10 utes while maintaining the temperature at about 15 C. or less. The sponge-forming mass is then deposited into suitable forms and the viscose coagulated and the cellulose regenerated in the manner set forth above. This may be done by steeping the closed forms into boiling water or into a boiling sodium sulfate solution for the required time, by subjecting them to an atmosphere of high pressure steam in an autoclave, or by raising the temperature of the mass by passing a heavy electrical current therethrough, preferably an alternating current. During the coagulation process, the sodium sulfate decahydrate crystals liquify and a good part of it flows from the mass leaving the corresponding pores. The coagulated blocks are then washed in hot water at approximately 95 C. for hour to remove the remaining sodium sulfate decahydrate and most of the contaminants and the washed blocks are then bleached with a water solution containing about 1 gram per liter chlorine in the form of sodium hypochlorite, for approximately 1 hour. The bleached blocks are then treated with a hot oxalic acid solution concentration, approximately 2 grams per liter, for approzdmately 1 hour, and again washed to remove traces of acid. The blocks are then impregnated with a suitable humectant such as glycerin, polyethylene glycol, propylene glycol, urea or mixtures thereof and dried to the desired moisture content. lIt is important to note that by reason of the increased permeability and penetrability of the sponge the above purification and aftertreating time is approximately half that normally required.

The sponge block is then dried to the desired degree and cut and packaged in the usual manner. Sponges prepared in accordance with the specific example have a tensile strength of 30 to pounds per square inch in the direction of orientation of the grain and 15 to 20 pounds to the square inch normal to the direction of the orientation of the grain. The sponge possesses a water of absorption of 25 times its dry weight.

In accordance with another example of the present invention in the production of an improved sponge reinforced with cellulose pulp, approximately fifteen pounds of wood cellulose pulp in sheet form were mixed with 1 0 gallons of a 0.3% aqueous solution of Nopco GLN and tumbled for about 30 minutes in a stainless steel drum of 19 inches diameter and 30 inches length rotating at about 15 rpm. The pulp employed is a bleached paper type wood pulp marketed by the Rayonier (Iompany as Georgianier J and has an average fiber length exceeding one millimeter. It should be noted however that other types of cellulose pulp may be employed, for example, dissolving pulp, chemical pulp, bleached or semibleached pulp, and the pulp may be initially in bulk, sheet or slurry form. Moreover, thepulp may be advantageously subjected to a breaking or cutting operation prior to its admixture with the wetting agent solution.

The mixture of the pulp and the wetting agent solution is introduced into about 680 pounds of viscose having a composition of 8% cellulose and 5 /2% total alkalinity and produced in the manner described above and having similar properties thereto and is admixed in the above manner for about 30 minutes. Thereafter, 1900 pounds of sodium sulphate decahydrate crystals are added and the mixing continued for about 10 minutes. The resulting mass is then coagulated, handled, and after treated in the manner above set forth. It should be noted that the process parameters and the various ingredients and their properties may be modified as set forth in connection with the earlier example and as previously described. Where the cellulose pulp is substantially the sole reinforcing agent it should be present in from 10% to and preferably from 20% to 40% by weight of the cellulose content of the viscose which is subsequently regenerated. For example, if the final sponge product contains pounds cellulose regenerated from the viscose, the reinforcing cellulose pulp fibers should be present in from E11 6 10 to 50 pounds and preferably between 20 and 40 pounds.

In the example last described, the pulp may be replaced in part by flax or hemp or other fibers having an average length preferably between /s and 1 /2 inch and the same procedure followed. For example, 1 pounds of pulp and 5 pounds of flax cut to a length of inch are substituted for the 15 pounds of pulp of the last example. it should be noted that since the cost of the cellulose pulp is between live and ten cents per pound while the cost of the cheapest acceptable conventional reinforcing fiber is between twenty and twenty five cents per pound, significant economies are realized by the use of the pulp in whole or in part. Furthermore many of the properties of the final sponge are enhanced with the use of the pulp as the reinforcing material while the strength thereof does not appear to be adversely affected. Sponge produced in the above manner wherein fifty percent of the normally employed flax fiber was replaced by the same quantity of pulp exhibits the same strength as the sponge containing as its reinforcing fiber 100% flax.

While there have been described and illustrated preferred embodiments of the present invention, it is apparent that numerous alterations and omissions may be made without departing from the spirit thereof.

What is claimed is:

1. The method of producing a regenerated cellulose sponge comprising the steps of first immersing a fibrous material into an aqueous solution of a surface active wetting agent of a concentration between about 0.1% and 1.0% and at a ratio of wetting agent solution to fibers of about 3:1 to 9:1, thereafter admixing said fibers and said wetting agent solution with a viscose solution and a pore-forming substance whereby to un formly disperse said fibers and said wetting agent solution and said poreforming substance throughout said viscose, said wetting agent being introduced into said solution in an amount between about 0.2% and 3.2% of the cellulose content of said viscose, and thereafter coagulating said viscose and regenerating the cellulose therein.

2. The method of producing a regenerated cellulose sponge comprising the steps of first immersing a cellulose pulp into an aqueous solution of a surface active wetting agent of a concentration between about 0.1% and 1.0%

and at a ratio of wetting agent solution to cellulose pulp of about 3:1 to 9:1, thereafter admixing said pulp and said wetting agent solution with a viscose solution and a pore-forming substance whereby to uniformly disperse the pulp fibers and said wetting agent solution and said pore-forming substance throughout said viscose, said wetting agent being introduced into said solution in an amount between about 0.2% and 3.2% of the cellulose content of said viscose, and thereafter coagulating said viscose and regenerating the cellulose therein.

3. The improved method in accordance with claim 1, wherein said wetting agent is selected from the class consisting of lauryl alkylcl amide, and diethanolamine of caproic acid.

4. The improved method in accordance with claim 1, wherein said viscose has a cellulose content of approximately 6% to 8% and an alkalinity of approximately 5% to 7% 5. The method in accordance with claim 1 wherein said fibrous material is selected from the class consisting of cellulose pulp and cut fibers of hemp, flax, nylon, cot ton and rayon.

6. The method in accordance with claim 1 wherein said pore forming substance is sodium sulfate decahydrate.

7. The method in accordance with claim 2 wherein said cellulose pulp is present in from 10% to by weight of the cellulose content of said viscose.

8. The method in accordance with claim 2 wherein said cellulose pulp is selected fromthe class consisting of paper grade wood pulp and dissolving grade wood pulp, of bleached and semibleached types and in bulk, sheet and slurry forms.

9. The method in accordance with claim 2 including admixing with said pulp carrying wetting agent solution cut fibers selected from the class consisting of natural and synthetic fibers.

References Cited in the file of this patent UNITED STATES PATENTS 2,077,412 Herzog et al. Apr. 20, 1937 2,295,823 Banigan et al Sept. 15, 1942 2,341,509 Bley Feb. 15, 1944 2,495,237 Petiton Jan. 24, 1950 2,853,395 Osborn Sept. 23, 1958 

1. THE METHOD OF PRODUCING A REGENERATED CELLULOSE SPONGE COMPRISING THE STEPS OF FIRST IMMERSING A FIBROUS MATERIAL INTO AN AQUEOUS SOLUTION OF A SURFACE ACTIVE WETTING AGENT OF A CONCENTRATION BETWEEN ABOUT 0.1% AND 1.0% AND AT A RATIO OF WETTING AGENT SOLUTION TO FIBERS OF ABOUJT 3:1 TO 9:1, THEREAFTER ADMIXING SAID FIBERS AND SAID WETTING AGENT SOLUTION WITH A VISCOSE SOLUTION AND A PORE-FORMING SUBSTANCE WHEREBY TO UNIFORMLY DISPERSE SAID FIBERS AND SAID WETTING AGENT SOLUTION AND SAID POREFORMING SUBSTANCE THROUGHOUT SAID VISCOSE, SAID WETTING AGENT BEING INTRODUCED INTO SAID SOLUTION IN AN AMOUNT BETWEEN ABOUT 0.2% AND 3.2% OF THE CELLLULOSE CONTENT OF SAID VISCOSE, AND THEREAFTER COAGULATING SAID VISCOSE AND REGENERATING THE CELLULOSE THEREIN. 